Yes, the 5.9(.1) series had the 'update all packages' disable due to an inadequately managed repository. There has been lots of work in the repository since the release of 5.9(.1) and updates should work better. You can still perform a full system upgrade (non-rolling, of course) using slapt-get, however there is potential to break some things.

Again, the 'testing' repo for the 5.9(.1) series was not managed as effectively as the 6.0 repo therefore some updates did not move from 'testing' to 'patches' or 'extra' as quickly as they probably should have.